Roofing products are often divided into three broad groups: shingles, roll roofing, and underlayment. Shingles and roll roofing typically function as outer roof coverings designed to withstand exposure to weather and the elements. Typically, the underlayment is first laid on the roof deck, and then the outer roofing covering (e.g., shingles or roll roofing) is installed on top of the underlayment.
Asphalt shingles are the most commonly used roofing materials. Shingles and roll roofing generally contain the same basic components, which provide protection and long term wear associated with asphalt roofing products. These components include a base substrate material made from an organic felt or fiberglass mat which serves as a matrix to support the other components and gives the product the required strength to withstand manufacturing, handling, installation, and service in the intended environment. An asphalt coating formulated for the particular service application is often applied to the base substrate material to provide the desired long-term ability to resist weathering and to provide stability under the anticipated temperature extremes. An outer layer of mineral granules is also commonly applied to the asphalt coating to form a surface exposed to the weather which shields the asphalt coating from the sun's rays, adds color to the final product and provides fire resistance.
Typically, shingles are installed on a roof deck such that the shingles are in a row from left to right and the lateral edges of the shingles in the row are contiguous with each other so as to abut each other, i.e. their lateral edges are adjacent to one another. Each row represents a course and the shingles are applied in overlapping courses on the roof deck, wherein the buttlap portion of a subsequent course is placed on the headlap portion of a previous course. The headlap portion of a conventional shingle is at least as wide as the buttlap portion of the shingle so that when the shingles are installed on a roof deck in overlapping courses, the entire buttlap portion of a subsequent course has headlap beneath it. If the shingle has tabs and openings in the buttlap portion, it is typical that at least two inches of the headlap portion of the subsequent course also has headlap from the previous course of shingles beneath it. This manner of installation prevents leakage to the roof deck where the lateral edges of the shingles abut each other and, in the case of tab shingles, where the openings in the buttlap are located.
In a typical prior art roofing system, contiguous shingles in a row abut each other at their lateral edges. Thus, when the shingles are exposed to wet weather, it is possible that leakage can occur at the region where the shingles abut. To prevent that, overlapping subsequent rows of shingles are installed in an offset pattern and each shingle's headlap portion is at least as wide as the buttlap portion. Thus, when the shingles are applied to the roof in a plurality of courses and the buttlap portion of a second course of shingles is laid over the headlap portion of a first row of shingles there is always headlap present underneath the regions where the contiguous shingles in a row abut. Any water penetrating the places where lateral edges of shingles abut contacts the headlap rather than the roof deck.
In a typical prior art roofing system using shingles with a tabbed buttlap portion, overlapping courses of shingles are installed such that they generally overlap each other to provide at least two inches of headlap across the entire headlap from the previous course of shingles underneath the headlap portion of the subsequent course. Such headlap overlap helps ensure that water contacting the headlap through the openings in the subsequent course does not contact the roof deck. Such headlap overlap is also usually required by building code.
As energy costs rise, the cost of petroleum-based materials, such as asphalt, and transportation expenses often rise as well. The amount of material employed in a shingle can contribute to costs of the shingle and the overall weight of the shingle, which also affects transportation costs. Certain installation requirements, such as a two inch headlap overlap for single layer shingles with a tabbed buttlap portion, constrain the possible dimensions for a shingle. Decreasing the amount of asphalt, substrate, and other materials required to make a shingle while maintaining the equivalent performance and coverage area, can reduce both material costs and transportation expenses to deliver such shingles.
Various shingles have employed, for aesthetic purposes, non-straight edge contours. U.S. Pat. No. 1,345,627 describes single layer roofing shingles to be arranged in overlapping courses. The shingle may have non-straight longitudinal edge contours, which shadow each other on either side of the shingle such that the width of the shingle is constant across the length of the shingle. The contour of the shingle, along with other features, operates to optically simulate various appearances including curved tiles.
U.S. Pat. No. 2,272,032 describes single layer asphalt roofing shingles with varying cross-sectional thickness to be arranged in offset overlapping courses. The shingle has longitudinal zigzag edge contours, which shadow each other on either side of the shingle such that the width of the shingle is constant across the length of the shingle. When the courses are installed, the thicker portions of a subsequent shingle “nest” in the thinner portions of the previously installed shingle to provide the protection qualities of more heavily coated roofing material.
U.S. Pat. No. 4,274,243 describes a laminated asphalt roofing shingle to be arranged in overlapping courses to optically simulate tiles. The shingle has a headlap portion with a generally straight edge and a butt portion with a generally continuously curving sinuous butt edge and an underlay portion with a matching generally continuously curving sinuous butt edge.
U.S. Pat. No. 4,333,279 describes strip or tabbed single layer asphalt shingles. The shingles have a headlap portion with a generally straight edge and a butt portion with a jagged, nonuniform butt edge.
U.S. Pat. No. 5,939,169 describes a composite shingle with a headlap portion, a buttlap portion that is divided into uniformly spaced apart tabs with curved or straight bottom edges or crimped corners, and an elongated backup strip that underlays the buttlap portion and conforms in outline to the bottom edge of the tabs and extends below the tabs at a distance equal to the spaces between the tabs so as to form a uniform border around the tabs.
U.S. Pat. No. 6,058,670 describes a laminated shingle with a headlap portion, a buttlap portion that is divided into uniformly spaced apart tabs with curved or straight bottom edges or crimped corners, and an elongated top strip that overlays the headlap portion and has a lower edge that duplicates or mirrors the sequence of the lower edge of the tab so as to allow a uniform strip border surrounding each tab upon installation.
U.S. Pat. No. 6,698,151 describes a laminated asphalt roofing shingle to be arranged in overlapping courses to simulate tiles. The shingle has a headlap portion with a generally straight contour and a buttlap portion with tabs. The tabs and openings between the tabs may have generally curved bottom edges. The buttlap portion also includes an underlay portion, which may have generally curved edges that may be coextensive with the curved bottom edges of the tabs.
Each of the above-referenced patents is incorporated herein by reference for all purposes within this application.